class UnionFind {
  private int[] parent;
  UnionFind(int size) {
    parent = new int[size];
    // 初始化，将每个节点的根节点指向自己
    for (int i = 0; i < size; i++) {
      parent[i] = i;
    }
  }
  
  public void join(int a, int b) {
    int aRoot = find(a);
    int bRoot = find(b);
    
    if (aRoot == bRoot) {
      return;
    }
    
    parent[aRoot] = bRoot;
  }
  
  public int find(int a) {
    if (parent[a] == a) {
      return a
    }
    
    parent[a] = find(parent[a]);
    return parent[a];
  }
  
  public boolean isSame(int a, int b) {
    int aRoot = find(a);
    int bRoot = find(b);
    
    return aRoot == bRoot;
  }
}